1. Field of the Invention
The present invention relates to an image forming optical system, and an image pickup apparatus and an identification apparatus using the system.
2. Description of the Related Art
In entering or going out of a facility where security is regarded as important, or in a case of log-in to an information system or the like, confidentiality has heretofore been protected using an IC card or password. However, illegal actions such as forgery and spoofing often cause leakage of information and hacking, and there is a demand for an identification method having higher security. Therefore, in recent years, biological identification (biometrics) has prevailed in which a person is identified using person's physical features such as fingerprint, palm pattern, iris and vein.
As a technology concerning an optical system for such biological identification, there is proposed a technology described in Japanese Patent Application Laid-Open No. 8-334,691.
However, the system described in Japanese Patent Application Laid-Open No. 8-334,691 is an object-side telecentric optical system. Therefore, a lens diameter of a lens disposed closest to an object side increases depending on a size of an object surface, that is, a finger size. Any design for miniaturizing the optical system is not considered in Japanese Patent Application Laid-Open No. 8-334,691, and it is difficult to miniaturize the optical system.
As means for miniaturizing the optical system, there is a method of disposing a reflecting member in an optical path to bend the optical path. As technologies concerning the optical system in which the optical path is bent using the reflecting member, there are proposed, for example, Japanese Patent Application Laid-Open Nos. 2000-292,692, 51-62,053 and 11-205,664.
In the optical systems described in Japanese Patent Application Laid-Open Nos. 2000-292,692 and 51-62,053, each of the systems is constituted by arranging a first lens unit, the reflecting member for bending the optical path and a second lens unit in order from the object side.
Moreover, the optical system described in Japanese Patent Application Laid-Open No. 11-205,664 is constituted by arranging the first lens unit and the reflecting member for being the optical path in order from the object side.